The present invention relates to an analog/digital converter used, for example, in a digital scale with a load cell or the like.
In conventional analog/digital converters which include integrators and operate on a single DC power source voltage, a voltage equal to 1/2 the power source voltage is supplied as a reference voltage to the integrator. Hence, a voltage generator capable of generating a voltage equal to 1/2 the source voltage is necessary. A resistor type voltage divider is often used to constitute such a voltage generator. In order to keep down the power consumption of the voltage divider, however, its resistance is set at a relatively high value. The resistance of the voltage divider is set particularly high when a battery is used as the DC power source.
In this kind of A/D converter, using a simple resistor type voltage divider to generate a voltage equal to 1/2 source voltage VD, the impedance of the power source as viewed from the input side of the integrator is high, and the voltage VD/2 may fluctuate greatly. As a result, it has been impossible to construct a high-precision A/D converter.